Manufacture of acetic acid



April 18, 1933.

S. R. MERbEY ET AL MANUFACTURE OF ACETIC ACID Filed Jan. :51, 1931 IUZMUM xva yup-.43

INVENTOR5 SYLVAN R MERLE! BY OTTO $FZ\EG rent to both gases introduced into the tower, thus bringing them into intimate contact to produce larger yields of carbyl sulfate. The carbyl sulfate is withdrawn from the tower 5 through a valved conduit 12 into an insulated receivlng tank 14. melting point of about 80 6., and in order to keep it above its melting point and in liquid phase the pipe lines conducting it are well insulated. As soon as a suilicient quantity of carbyl sulfate has collected is withdrawn through a valve controlled pipe 16 and passed by a pump 18 and insulated pipes 20 and 22 into the upper portion of the tower in which the sulfate acts to maintain intimate contact between the gases therein.

If pure ethylene the tower there will be no spent gases escaping from thetop of the tower since the com- I 349 bination between the sulfur trioxide and the ethylene is practically quantitative. However, if tail gases containing ethylene obtained in the cracking of petroleum are introduced into the tower, the spent gases escapin overhead will mechanically carry off carb sulfate. The tail gases therefore, leavln the tower 4 are conducted through a vapor ine 24 into a scrubber 26 in which they pass countercurrent to water introduced through a pipe 28. The washed gases pass off through an outlet 30. The water, referably hot, hydrolyzes whatever c'arb sulfate is caried over with the gases, to orm a solution of isethionic and sulfuric acids which is withdrawn into a receiver tank 32. If any ethylene oxide is formed in tower 4, it would react with sulfur trioxide to form glycol sulfate, a heavy non-volatile liquid which is recovered in thecarbyl sulfate solution. From this the glycol sulfate would be converted to ethylene oxide or glycol when treated with caustic in the reaction mixer 42, the

ithyilene oxide or glycol being vented over- The scrubbing tower may be similar in construction to tower 4 being provided with bubble cap trays 34 and coils35 through which a cooling or eating medium may be circulated to control the temperature during the hydrol-- ysis of the carbyl sulfate. The scrubber is also insulated to prevent heat loss by radiation. A hot brine solution at temperatures of 95 to 115 C. passing through the coils has been found best to control the reaction during the hydrolysis of the carbyl sulfate. 4

' When a suflicient accumulation of carbyl sulfate has been made in receiver 14,1a batch of this material is conducted from pipe 20 through pipe 38 and branch pipe 40 into a I reaction mixing chamber 42. The mixer42 is one of a pair of mixers 42 and 44 which are provided with the usual mixing blades and *also with a jacket so that they may be either heated or cooled in accordance with as the desire of the operator or the necessity for ionic acid collected in The carbyl sulfate has a in the tank 14 it has been introduced into the particular reaction. To the batch of carbyl sulfate in mixer 42 may be added the accumulation of dilute sulfuric acid and isethreceiver 32, through a valved 46. In order to completely bydrolyze the carbyl sulfate in the reaction mixare additional quantities of water are introduced through pipe 48. The resultant mixture in chamber 42 comprises sulfuric acid and isethionic acid.

This mixture isnext neutralized with a caustic soda solution which is introduced into chamber 42 through a pipe 50. In neutraliz ing the mixture considerable uantities of sodium sulfate are formed in a dition to sodium isethionate. The solution is then concentrated and cooled to crystallize the sodium sulfate. The mixture containing sodium sulfate is conducted through a valved ipe 52 and a filter 54 where the sodium su fate is separated and removed from the sodium isethionate which remains in solution and is pumped by means of a pum 56 and valved pipe 58 into the second reaction chamber 44.

nthe reaction chamber 44 the mixture is concentrated to about half its original volume by applying heat to the jacket of the con- The

line 60, through a condenser 62 and the densate conducted into a receiver water collecting in receiver 64 may charged through a valved outlet 66. As the mixture in tank 44 reaches the proper concentration, it is raised to a temperature of about 155 C. at which time a quantity of ordinar commercial lime (calcium oxide) is adde through conduit 68 and an excess of caustic soda solution is added through conduit 70.

The addition of concentrated caustic soda to the sodium isethionate causes the conversion of the latter into sodium acetate.

During the treatment chamber 44 a second batch ofcarbyl sulfate has been hydrolyzed in chamber 42 and is now conducted through pipes 52 and 58 into chamber 44, in which it is used to neutralize the reaction mixture therein. In fact sulficient quantities of the acid mixture are introduced to make the mixture in chamber 44 acid and thereby convert the sodium acetate into acetic acid.

The acetic acid in chamber 44 is preferably removed by distillation, the vapors being conducted through vapor line 60 and condensed in condenser 62. In this distillation substantial quantities of water, as well as sulphur dioxide are removed and conducted over with the acetic acid. The condensed ace-' be disinto a stripping tower 71 in which theliquid flows down over a series of trays countercurrent to an inert gas, such as air or carbon ilioxide, introduced through a pipe 72. The

ower portion of the tower 71 may be maintained at a temperature such that no substantial amount of the sulfur dioxide will re-' I main dissolved in the acetic acid mixture, but

- the reaction mixture through a valved at a temperature below the boiling point of the acetic acid. The purified acetic acid is withdrawn to storage through a valved pipe 74.

The mixture remaining in the reaction chambered now comprises a more or less concontra residue of sulfuric acid and isethionic acid, which is neutralized by introducing a caustic soda solution throuh a pipe 70. The sodium sulfate and .10: lsethionate solution produced by neutralization is concentrated to crystallize the sodium sulfate which is filtered ofi by conducting r 78 and filter 54, the filtrate containing 1' s rum isethionate being conducted by pump 56 and a valved pipe 80 into the first mixer 42, where the'steps of the process are repeated on the sodium isethionate. 1

In treating the solution in the mixer, lime may he added through conduit 82 and the vatill ,pors conducted from the chamber during the distillations throu h valved vapor line 84 which connects wit condenser 62. 1 J

From the above description, it is evident that the-process included by the present in. vention is capable of converting relatively inexpensive ethylene contained in cracking still gases into a relatively more valuable product by the use of ordinary chemicals such as sulfur trioxide and alkalies. An important feature of the process also includes the use of the acid solution produced in one operation for neutralizing and converting so-- dium acetate produced in another step of the process into acetic acid. These reatures' greatly lessen the expense involved in the menu acture of acetic acid.

In describing the process of the present invention tworeaction chambers were referred to, but it is to he understood that additional chambers may be used and at the same time maintain the series of operations outlined.

in the resent process, the quantity of sulfur trioxide contacted with ethylene is only such that there never is any free sulfur trioxide carried overhead from the reaction tower.

It is understood that the acetic acid resulting from the acidification of the alkaline mixture containing from the'resu tant mixture in any manner other than that described herein without departing from the scope of the invention.

Having thus described the invention in its prefer-r42 form what is claimed as new is:

1. The process of making acetic acid, which sodium sulfate in the neutralized an acetate may be separated sultant carbyl sulfate from the bottom of said zone and recycling the same through said zone, cooling and hydrolyzing carbyl sulfate from said zone, neutralizing the h drolyzed solution with caustic soda, crystallizing the solution, fi tering the solution free of precipitated sodium sulfate, heating and concentrating the filtrate, adding lime and an excess of a solution of caustic soda to the mixture while vigorously stirring the same, adding a solution containing a mixture of isethionic and sulfuric acid to the mixture to acidify the same, distilling off the resulting acetic acid and collecting the condensed acetic acid.

2. The process of manufacturin Y acetic acid, which comprises contacting su fur trioxide with cracked petroleum vapors containing ethylene to form carbyl sulfate, collecting the same and recycling it through said contact zone, Withdrawing part of the collected'carbyl sulfate,'cooling.and hydrolyzing with hot water to form a mixture containing isethion ic and sulfuric acids, neutralizing said acids with caustic soda, crystallizing and filtering 0d the sodium sulfate from said solution, concentrating thefiltrate containing so dium isethionate, raising the temperature of the filtrate to about 150 (1, adding lime and an excess of a solution of caustic soda with constant stirring to form an alkaline solution containing sodium acetate, acidifying to produce a mixturecontaining acetic acid, and then distilling over the acetic acid from the mixture.

3. The process of manufacturing acetic acid, which comprises, hydroyzing carbyl sulfate with suificient water to form a mixture containing isethionic and'sulfuric acids while controlling the heat of reaction resulting from the hydrolysis, neutralizing said mixture with a caustic soda solution to form a mixture containing sodium sulfate and sodium isethionate, cooling the mixture to crystallize therefrom the sodium sulfate, filtering oil the crys talline sulfate, collecting the filtrate and coin centrating it to about one ha'f of its original volume, raising the temperature of the concentrate to about 155 (3., adding a small quantity of lime, then an excws of a solution of caustic soda to said concentrate with constant stirring, reducing the temperature on the resultant mixture to about 120 (1, acidifying the mixture with a solution containing isethionic and sulfuric acids, then taking ed the resultantfacetic acid from the mixture.

4. The process of manufacturing acetic acid, which comprises hydrolyzing earbyl sul fate to form a mixture containing isethionic and sulfuric acids, neutralizing said mixture to form sodium isethionate and sodium sulfate, concentrating and cooling the mixture to crystallize out the sodium sulfate from said Mill Elli

initial volume,

filterin off the sodium sulfate, confiltrate to about one-half its raising the temperature to about 155 (1., then adding an excess of concentrated caustic soda solution to form sodium acetate, acidifying the mixture with a solution containing isethionic and sulfuric acids, and separating the resultant acetic acid from the mixture.

5. The process of manufacturing acetic acid, which comprises hydrolyzing carhyl sulfate to form a mixture containing isethionic. and sulfuric acids, neutralizing said mixture to form an isethionate and a sulfate, adding an excess of concentrated caustic soda solution to,convert the isethionate to sodium acetate, acidifying the resulting mixture to mixture, centrating the I convert the sodium acetate to acetic acid,

- the liquid portion containing sodium isethiand separating the resultant acetic acid from the mixture.

6. The process of manufacturing acetic acid, which comprises hydrolyzing carloyl sulfate to produce an acid solution containing isethionic and sulfuric acids, ing said solution,

evaporating, cooling and crystallizing from the resultant mixture any sulfates formed, filtering out the sulfates,

collecting the filtrate and concentrating it to a desired volume, raising the temperature of the concentrate, adding lime and an excess of caustic solution to form sodium acetate, adding isethionic and sulfuric acids to form a solution containing acetic acid, and separating out the acetic acid.

7. The process of making acetic'acid, which comprises hydrolyzing carbyl sulfate with water, cooling it to temper the heat of reaction between the water and the carbyl sulfate, neutralizing the resulting acid solution with caustic soda, crystallizini out the formed sodium sulfate from t e formed sodium isethionate in solution, filtering ofi onate, concentrating and treating the saline with an excess of caustic solution at about 155 C. with constant stirring, reducing the tem erature of the mixture to about 120 (3.,

adding an excess of an acid solution to neutralize the caustic added to said mixture and to convert the isethionate to acetic acid, and

recovering the acetic acid from the mixture.

8. The process of making acetic acid, which comprises hydrolyzing carbyl sulfate while tempering the heat evolved during the re-v action to form isethionic and sulfuric acids,

with constant agitation a small neutralizacid which includes the contacting of sulfur trioxide with cracked petroleum vapors containing ethylene in a contact zone to form carbyl sulfate, the steps which com rise passingvapors and gases containingcar ylsulfate from said zone countercurrent to a stream of water to hydrolyze the carbyl sulfate, colleeting the resulting isethionic and sulfuric acids formed by said hydrolysis, neutralizing the acids with alkali solution to form a mixture of isethionate and sulfate, adding quantity of lime and an excess of a caustic soda solution to form an alkaline solution containi sodium acetate, acidifying the solution on separating the resulting acetic acid t erefrom.

In testimony whereof I aflix my signature.

SYLVAN R. MERLEY.

I afix my signature.

one seems.

In testimony whereof,

neutralizing said acids with an alkali ,solution to form a mixture containing isethionate and sulfate, crystallizing and separating the sulfate from the isethionate, concentrating the isethionate solution, raisin the temperature on the concentrate, ad ing an excess of alkali solution with constant stirring, acidifying to form acetic acid, then collecting the acetic acid formed from said mixture.

9. In the process of manufacturing .acetic' 

